Etomidate
Etomidate is a short-acting intravenous anaesthetic agent used for the induction of general anaesthesia and sedation. It is classed as a non-barbiturate hypnotic.
It is metabolised in the liver. The half-life of etomidate is around 75 minutes but recovery from etomidate is rapid with little residual depression as a result of extensive redistribution and rapid metabolism. At the typical dose, anaesthesia is induced for approximately 5–10 minutes with onset 30-60 seconds after administration.
Cautions and contraindications
Etomidate is associated with rapid recovery without a hangover effect. Etomidate causes less hypotension than thiopental sodium and propofol during induction. It produces a high incidence of extraneous muscle movements, which can be minimised by an opioid analgesic or a short-acting benzodiazepine given just before induction.
There are four commonly used induction agents in the UK. These are summarised in the table below:
Mechanism of action
Etomidate binds to GABAA receptors and prolongs the post-synaptic inhibitory effect of GABA in the thalamus.It is metabolised in the liver. The half-life of etomidate is around 75 minutes but recovery from etomidate is rapid with little residual depression as a result of extensive redistribution and rapid metabolism. At the typical dose, anaesthesia is induced for approximately 5–10 minutes with onset 30-60 seconds after administration.
Side effects
Common side effects:- Apnoea
- Hypotension
- Movement disorders (extraneous muscle movements can be minimised by an opioid analgesic or a short-acting benzodiazepine given just before induction)
- Nausea & vomiting
- Respiratory disorders
- Skin reactions
- Vascular pain (injection pain can be reduced by giving an opioid analgesic just before induction)
Cautions and contraindications
- Acute circulatory failure (shock)
- Adrenal insufficiency
- Acute porphyrias
- Cardiovascular disease
- Elderly
- Fixed cardiac output
- Hypovolaemia
Adrenal insufficiency
Etomidate suppresses adrenocortical function, particularly during continuous administration, and it should not be used for maintenance of anaesthesia. It should be used with caution in patients with underlying adrenal insufficiency e.g. patients with sepsis.
Etomidate suppresses adrenocortical function, particularly during continuous administration, and it should not be used for maintenance of anaesthesia. It should be used with caution in patients with underlying adrenal insufficiency e.g. patients with sepsis.
Comparison to other induction agents
Etomidate is associated with rapid recovery without a hangover effect. Etomidate causes less hypotension than thiopental sodium and propofol during induction. It produces a high incidence of extraneous muscle movements, which can be minimised by an opioid analgesic or a short-acting benzodiazepine given just before induction.
There are four commonly used induction agents in the UK. These are summarised in the table below:
| Drug | Key Points | Dose | Side effects |
|---|---|---|---|
| Propofol 1% |
| 1.5-2.5 mg/kg | Hypotension Respiratory depression Pain at site of injection |
| Ketamine |
| Initially 0.5-2 mg/kg Typical IV dose is 1.5mg/kg | Tachycardia Hypertension Laryngospasm Unpleasant hallucinations Nausea and vomiting Hypersalivation Increased intracranial and intraocular pressure Nystagmus and diplopia Abnormal movements Skin reactions |
| Thiopentone (thiopental sodium, sodium pentothal) |
| Adult: 3-5 mg/kg Child: 5-8 mg/kg Doses halved in hypovolaemia | Venodilation Myocardial depression Hypotension Contraindicated in: Acute porphyrias Myotonic dystrophy |
| Etomidate |
| 0.15-0.3 mg/kg | Injection site pain Movement disorders Adrenal insufficiency Apnoea Contraindicated in: Sepsis (due to adrenal suppression) |